Bizarre spiked tree has ties to ice-age Missouri

Nov. 14, 2013

A wicked tangle of 2-inch thorns protects the trunk of this honeylocust tree at Bennett Spring State Park. Some theorize the spikes kept ice-age herbivores from munching the bark. / Wes Johnson/News_Leader

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A wicked tangle of 2-inch thorns protects the trunk of this honeylocust tree at Bennett Spring State Park. Some theorize the spikes kept ice-age herbivores from munching the tree's bark. / Wes Johnson/News-Leader

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Our trek along the Blue Trail at Bennett Spring State Park led us to a small grove of bizarre-looking trees, the likes of which I had not seen before.

Growing in flat bottom land, the trees’ trunks were festooned with wicked-looking mats of 2-inch-long needle-sharp spikes that would keep even squirrels at bay. Why were they growing there and nowhere else? And why the spikes?

I turned to an expert and the answer, I discovered, takes us back to the ice age.

“It’s a tree that’s native to Missouri and you’re correct ... those thorns are large and painful looking. There’s a real interesting theory about why those thorns are so large.... I read about it several years ago. Granted, it’s just a theory and when I posed this to a couple of foresters, they said they had never heard this before, but nevertheless, this theory sounds logical, reasonable.

“In a nutshell, the theory is based on how everything in an ecosystem has a purpose — and there doesn’t seem to be any earthly reason why a tree should have thorns this large unless these trees are botanical remnants of ecosystems that no longer exist.

“Proponents of this theory say to look at thorn trees around the world: The places you’ll find trees with the biggest thorns are regions where large, tree-browsing mammals reside — far larger than deer or any other type of herbivore native to Missouri. In these areas, the large thorns are an effective defense mechanism to protect the trees.”

Skalicky notes the unusual thorn arrangement on the honeylocust trunk, but no thorns growing next to the sweet-tasting seed pods that appear in summer and are a source of food for wild animals.

“Some biologists have combined the size of the thorns with their placement to come up with an interesting theory: They say the true purpose of the honeylocusts’ large thorns was to prevent mammoths, mastodons, giant sloths and other large tree browsers from chewing the bark off the tree. Conversely, a lack of thorns around the seed pods encouraged these large herbivores to chomp on the pods. This gave the tree a broader means of seed dispersal because the seeds could be spread in the animals’ feces.

“Hedge trees (also called Osage orange or Bois D’Arc trees) fall into the same category. It’s theorized the reason hedge apples are so big and showy is because they evolved to become obvious food for mammoths, mastodons, sloths and other large prehistoric tree browsers that played a key role in distributing their seed through the animals’ feces.”

Skalicky said honeylocust trees today are found throughout the Ozarks and are a valuable resource both for animals and humans.

“If you can maneuver through the thorns, the wood is very good firewood... it’s very dense and burns quite hot,” he wrote.